Out-of-bounds write in Exim - CVE-2020-28022

Vulnerability identifier: #VU52867

CSH Severity: High

CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2020-28022

CWE-ID: CWE-787

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a boundary error when processing untrusted input within the extract_option() function. A remote attacker can create a specially crafted message to the mail server, trigger and out-of-bounds write or read error and execute arbitrary code on the target system.

Exim
Amazon Linux AMI
Gentoo Linux
Ubuntu
exim4 (Debian package)
exim4-daemon-light (Ubuntu package)
exim4-daemon-heavy (Ubuntu package)
exim4-base (Ubuntu package)
exim

Install updates from vendor's website.

Exim - update to 4.94.2
exim4 (Debian package) - update to 4.92-8+deb10u6
exim4-daemon-light (Ubuntu package) - addressed in versions 4.86.22ubuntu2.6+esm1, 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-daemon-heavy (Ubuntu package) - addressed in versions 4.86.22ubuntu2.6+esm1, 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim4-base (Ubuntu package) - addressed in versions 4.86.22ubuntu2.6+esm1, 4.90.1-1ubuntu1.8, 4.93-13ubuntu1.5, 4.94-7ubuntu1.2, 4.94-15ubuntu1.2
exim - update to 4.92-1.33

• http://seclists.org/oss-sec/2021/q2/91

• Multiple vulnerabilities in Exim
• Gentoo update for Exim
• Debian update for exim4
• Ubuntu update for exim4
• Ubuntu update for exim4
• Amazon Linux AMI update for exim